Which of the following findings are not diagnostic for diabetes mellitus: hemoglobin A1c >5.5%, fasting plasma glucose ≥126 mg/dL, random plasma glucose ≥200 mg/dL with classic hyperglycemic symptoms, ketosis, or 2‑hour oral glucose tolerance test glucose ≥150 mg/dL?

Which Findings Are NOT Diagnostic for Diabetes Mellitus

Options a, d, and e are NOT diagnostic criteria for diabetes mellitus according to current American Diabetes Association standards.

Established Diagnostic Criteria for Diabetes

The American Diabetes Association defines four valid diagnostic criteria 1, 2:

• HbA1c ≥6.5% (not >5.5%) performed in an NGSP-certified laboratory 1, 2
• Fasting plasma glucose ≥126 mg/dL after at least 8 hours of fasting 1, 2
• 2-hour plasma glucose ≥200 mg/dL during a 75-gram oral glucose tolerance test 1, 2
• Random plasma glucose ≥200 mg/dL in patients with classic hyperglycemic symptoms (polyuria, polydipsia, unexplained weight loss) 1, 3

Analysis of Each Option

Option a: HbA1c >5.5% - NOT DIAGNOSTIC

• An HbA1c of 5.5% falls well below the diagnostic threshold of ≥6.5% 1
• HbA1c values of 5.7-6.4% indicate prediabetes (increased risk for diabetes), not diabetes itself 1, 2, 3
• This threshold is too low and would misclassify many normal individuals as diabetic 1

Option b: Fasting glucose ≥126 mg/dL - DIAGNOSTIC ✓

• This meets the established diagnostic criterion when confirmed on a separate occasion 1, 2

Option c: Glucose ≥200 mg/dL random sample with symptoms - DIAGNOSTIC ✓

• This is valid when classic hyperglycemic symptoms are present 1, 3
• Classic symptoms include polyuria, polydipsia, and unexplained weight loss 1, 3

Option d: Ketosis - NOT DIAGNOSTIC

• Ketosis is a metabolic state that can occur in diabetes but is not a diagnostic criterion for diabetes mellitus 1
• Ketosis can occur in other conditions including starvation, ketogenic diets, and alcoholic ketoacidosis
• While diabetic ketoacidosis represents a hyperglycemic crisis, the diagnosis of diabetes itself requires meeting glucose or HbA1c thresholds 1

Option e: Glucose ≥150 mg/dL at 2 hours OGTT - NOT DIAGNOSTIC

• The diagnostic threshold for the 2-hour OGTT is ≥200 mg/dL, not ≥150 mg/dL 1, 2
• A 2-hour value of 140-199 mg/dL indicates impaired glucose tolerance (prediabetes), not diabetes 1, 2, 3
• A value of 150 mg/dL falls in the prediabetes range and would miss the diagnosis 1, 3

Critical Confirmation Requirements

• In the absence of unequivocal hyperglycemia (hyperglycemic crisis with clear symptoms), two abnormal test results are required to confirm diabetes 1, 2
• These can be two results from the same test on different days, or two different tests above their respective thresholds 1
• This requirement prevents misdiagnosis due to laboratory variability or transient stress hyperglycemia 1, 3

Important Caveats

• HbA1c should not be used for diagnosis in conditions with altered red blood cell turnover: sickle cell disease, pregnancy (second/third trimesters), G6PD deficiency, hemodialysis, recent blood loss/transfusion, or erythropoietin therapy 1, 2
• In these situations, only plasma glucose criteria should be used 1
• Plasma glucose samples must be centrifuged and separated immediately after collection to avoid falsely low results from glycolysis 1, 2